[steverino]

It does seem as if machinists/builders in general (but particularly those that do not specialize in, or have adequate experience with Pontiac engines), will tend to err on a cautionary side as far as both 1) compression ratio, and 2) cam choice (particularly size/duration).

It seems that they try to "play it safe" and often do not make for satisfied customers !

I tend to agree with the "9.5 and under" (iron head) rule of thumb that my builder subscribed to (not that I had much choice), since I likely would not have gained noticeable power on the street , and it may have REALLY not worked with my current 274 cam

The cam is at least a bit easier to change after the fact (assuming no damage occurs from a lobe or bearing stress). While I do understand the builder using "caution" (perhaps inexperience) in recommending a xe268, the cam company (comp cams) as well as experienced and reputable builders recommending (although not directly on this forum) the same 268 cam for the same 9.0-9.5 iron head 455 made it a close call for me , a newbie to building Pontiac 455's at least, although I've owned and driven them for years

Kinda makes me wonder if anyone has a 455 (pont) with a 268 cam that is actually happy with it ?

[Cliff R]

There is no "playing it safe" by selecting a SCR at or less than 9.5 to 1, when you come along and put a really small cam in the engine on a tight LSA with really quick ramps designed to improve cylinder filling and improve low end power. That's what this thread is about, making piss-poor cam choices for HUGE engines with moderate compression. You can get into trouble very quickly doing this, and leave a BUTT LOAD of power on the table at the same time.......Cliff

[steverino]

This is part of the irony, many builders (even cam company) still believe that the smaller cam/lower compression ratio (9.0-9.5) is "safer", for street driveability, pump gas etc in the iron head 455

I do wonder if I were to call comp cams again (5-6 yrs later), and asked for advice on cam choice for this exact same build, if the xe268 would come out as their primary recommendation ?

[Steve C.]

"I do wonder if I were to call comp cams again (5-6 yrs later), and asked for advice on cam choice for this exact same build..."

Probably will depend on the cubicle the phone call is routed to. But I'll suspect they will probably regurgitate the use of the 995 valve spring !


.

[1966Lemans]

Man, this thread is really fascinating. A lot of things that the average joe would think of intuitively, are exactly the opposite.

But, what about a guy who has a street cruiser, that wants to be able to burn 87 octane? Say he has a TH350, stock converter and 2.93 rear end. If his goal is to have really good off-idle throttle response (with an occasional wheel spin), and never rev past 4500, are all these "bigger cam" recommendations still valid?

--- Jay

[72LuxuryLeMansLa.]

Originally Posted by 1966Lemans

Man, this thread is really fascinating. A lot of things that the average joe would think of intuitively, are exactly the opposite.

But, what about a guy who has a street cruiser, that wants to be able to burn 87 octane? Say he has a TH350, stock converter and 2.93 rear end. If his goal is to have really good off-idle throttle response (with an occasional wheel spin), and never rev past 4500, are all these "bigger cam" recommendations still valid?

--- Jay

I'm no expert but I would say yes. No one has to spin their car up to 6000 RPM just because it can.Use that small cam in a 455+ ci engine and near 3500-4500 RPM is exactly where it will blow up on you.

[ponchjoe]

Originally Posted by 1966Lemans

Man, this thread is really fascinating. A lot of things that the average joe would think of intuitively, are exactly the opposite.

But, what about a guy who has a street cruiser, that wants to be able to burn 87 octane? Say he has a TH350, stock converter and 2.93 rear end. If his goal is to have really good off-idle throttle response (with an occasional wheel spin), and never rev past 4500, are all these "bigger cam" recommendations still valid?

--- Jay

I've only put a few engines together but I'll bet the response you will get here is to run the 068 in a low comp 455. Search the threads, I had one started last fall/winter about a low buck 455 build.

[tom s]

I did a 9.5 455 with a summit 2801 and it was a huge pinger.Pumped 200,the owner had to use race gas.Car flew,I really wanted to pull the cover and retard it a couple degrees but he sold the car first.FWIW,Tom

[Matt Meaney]

Originally Posted by 1966Lemans

Man, this thread is really fascinating. A lot of things that the average joe would think of intuitively, are exactly the opposite.

But, what about a guy who has a street cruiser, that wants to be able to burn 87 octane? Say he has a TH350, stock converter and 2.93 rear end. If his goal is to have really good off-idle throttle response (with an occasional wheel spin), and never rev past 4500, are all these "bigger cam" recommendations still valid?

--- Jay

Yes.

as stated in this thread, the smaller, tighter LSA, cam with lower compression, is MORE octane sensitive. meaning, it is more likely to need a higher octane fuel to use this combo. just because the engine makes more power to a higher rpm, doesn't mean it's a dog at lower rpm. a 4.21 stroke is going to make torque, period. engine combos, like described in this thread, will work fine in front of a stock convertor and high gears. no, you won't see it's total potential at the drag strip, but it will move the car around with authority and you can incinerate the tires at will.

an often over looked and extremely important part of any cars overall drivability, (including it's running temperature) is having the carb and dist. dialed in properly.

[ponyakr]

The more I read of this thread, the more I am convinced that with 9:1 CR or more, the RA4 grind with Rhoads lifters will be VERY hard to beat with any other combination. I mean it'll idle smooth at 800rpm or lower, have plenty of vac for brakes, and make power from an idle to 5000rpm. What more could you ask of a hyd flat tappet cam, for street and mild bracket racing ?

It may not run the lowest ET, or make the most dyno hp, but I mean, ya'll go ahead and list exactly what cam & lifter combo you think is better, and why.

[71 T/A]

I doubt you can beat SD's Stump Puller HR cam for drivability and performance.

[ponyakr]

Originally Posted by 71 T/A

I doubt you can beat SD's Stump Puller HR cam for drivability and performance.

"...What more could you ask of a hyd flat tappet cam, for street and mild bracket racing ?..."



In my mind, roller cams and hyd flat tappet cams are not even in the same league. I think that has been well proven on the dyno and strip. They can use lobe shapes which are impossible for a flat tappet to follow.

But there are LOTS of guys who don't have the budget for a complete roller set up for their mild street 455.

So, maybe I oughta rephrase it, keeping the hyd flats, separate from the rollers.

[68azbird]

Originally Posted by 71 T/A

I doubt you can beat SD's Stump Puller HR cam for drivability and performance.

Friend had that in his 462 driveability yes. For performance it was a big turd.

[Matt Meaney]

the "perception" of performance, on the street, is a very subjection thing. one mans rocket ship, is another's can't get out of it's own way stone. on the other hand, just because one car may not have that rush of power feel to it, doesn't mean it's not out accelerating another that gives you that rush of power feel. or, vise versa.

ultimately, it only really matters that the owner is happy with the level of performance he has.

[PAUL K]

There are members on this board that have run low 11's in heavy street cars (one weighing over 4000 lbs.) using a 234/244 112 LSA HFT cam, cast iron heads and the street manners of a completely stock, well tuned Bonneville.
It would be interesting to see how much faster people have went using the Stump Puller cam with cast iron heads, or aluminum heads. Please share your combinations and results.

[PontGuy]

Now discussion is getting more into my territory.

I did a 9.5 455 with a summit 2801 and it was a huge pinger.Pumped 200,the owner had to use race gas.Car flew,I really wanted to pull the cover and retard it a couple degrees but he sold the car first.

Interesting. My 9.5:1 Lemans engine has a Melling 26204 cam in it. The .050 and lift specs are the same as a 2801. Seat timing is listed at 288/298 which is the same as the updated 2801 specs (older references are 272/282 for the 2801.) My engine pumps 180-190 but never a ping on 93 octane even with an aggressive timing curve. Its turned out to be a great choice for my vert street cruiser- very mild-mannered, but a serious tire shredder and the car ran a 13.6 on street tires with no prep the only time I took it to the track. Makes me wonder if there was a real change to the 2801 cam sometime recently.

Kinda makes me wonder if anyone has a 455 (pont) with a 268 cam that is actually happy with it ?

Not me. My T/A came with an XE268 in a 455 with 5C 350 heads so around 9.5:1 CR. It pumps 180 but I had to set the all-in timing down to 30 deg max to keep it from pinging at higher RPMs under load. After a bunch of tuning- new fuel system, new exhaust, and carefully tweaked advance curve it now runs pretty good. But overall the Lemans engine is still stronger and I've got to believe that having to take that much timing out is leaving a lot of power on the table. Now that I've got most of the other stuff out of the way a cam swap is quickly working its way toward the top of my list.

I've actually got a lot more experience with 350 and 400 engines. These are my first two 455's. But no doubt long lazy lobes are a lot easier on the valve train and they make a high-CR engine less gas-sensitive. I came to those conclusions myself long before internet forums.

I can see why the RAIV/Rhodes combination would work so well, but not convinced that I would want any valvetrain ticking at all in my very nicely restored T/A street car. Just one of the reasons that I left the cam swap for last.

[72LuxuryLeMansLa.]

Originally Posted by 68azbird

Friend had that in his 462 driveability yes. For performance it was a big turd.

You want to define "big turd" for us? According to SD Performance "In a recent dyno test this cam installed in a 464ci engine with 9.5 to 1 compression, a set of our 250-260cfm CNC ported #11 cast iron heads, CNC ported cast iron Q-jet intake and a prepped Q-jet carb made 503hp and 575+ lb/ft of torque on 91 octane."

In my world 575lb/ft and 503HP does not equate to a "big turd" but is a respectable car. WE ARE in the street section after all.

[Ben M.]

Originally Posted by 1966Lemans

But, what about a guy who has a street cruiser, that wants to be able to burn 87 octane? Say he has a TH350, stock converter and 2.93 rear end. If his goal is to have really good off-idle throttle response (with an occasional wheel spin), and never rev past 4500, are all these "bigger cam" recommendations still valid?

I'm actually getting real world here on this... I've got a 455 that I think needs a valve job at minimum and most likely has a bad lifter (or cam lobe) in a HEAVY wagon, 3.08 rear end, 100% street car that will never see the track and I want to run 87 octane, my AC, and power brakes. Rebuilding the original 4X-1H heads and putting another 066 cam in it seems like a waste of money and leaving potential power on the table. What do experts recommend here?

My logic for 87 octane isn't related to cost - more when you're traveling on the road 500 miles from home a bad tank of gas can really mess up your day.

[b-man]

Originally Posted by 1966Lemans

Man, this thread is really fascinating. A lot of things that the average joe would think of intuitively, are exactly the opposite.

But, what about a guy who has a street cruiser, that wants to be able to burn 87 octane? Say he has a TH350, stock converter and 2.93 rear end. If his goal is to have really good off-idle throttle response (with an occasional wheel spin), and never rev past 4500, are all these "bigger cam" recommendations still valid?

--- Jay

A 455 can absorb a pretty good-sized cam and have great low-end power, even one with what most would consider to be a very low compression ratio.

For your car with a stock converter and 2.93 cogs I wouldn't hesitate to use either the Summit 2802 or the Crower 60916 in a 455 with around 8.5:1 compression.

My own daily-driver 455 (462) had 8.2:1 compression at the most and ran on 87 octane just fine, using a TH400 - 13" Continental - 2.56 open rear. Built it with pretty much all stock parts along with the 068 cam. I picked the 068 partly because I wanted to see how well a mix of factory stock parts would run, also because of the highway-geared drivetrain, low-compression ratio and my intended usage - daily driving with the RPMs somewhere between idle and 2K 99% of the time:http://forums.maxperformanceinc.com/...22&postcount=4

Thinking back now I'd shoot for an engine that runs on 91 or 93 octane rather than 87, the very small fuel cost savings at fill-up time would be more than offset with better fuel economy going to higher compression using premium fuel. Added side benefit is better performance for essentially the same fuel cost.

[77 TRASHCAN]

Originally Posted by Ben M.

I'm actually getting real world here on this... I've got a 455 that I think needs a valve job at minimum and most likely has a bad lifter (or cam lobe) in a HEAVY wagon, 3.08 rear end, 100% street car that will never see the track and I want to run 87 octane, my AC, and power brakes. Rebuilding the original 4X-1H heads and putting another 066 cam in it seems like a waste of money and leaving potential power on the table. What do experts recommend here?

My logic for 87 octane isn't related to cost - more when you're traveling on the road 500 miles from home a bad tank of gas can really mess up your day.

I don't have a clue what size the chambers are on your 4X heads, But the 068 would be a minimalist cam choice to me for a 455.
You're not looking for the absolute power numbers, would be a great driver, not give up any low end rpm drive ability or MPG over a 066 cam, may make both better! As communicated here quite often, the awesome 068 cam can be used w/ stock springs.